What is the future worth of each given series of payments? (a) $8,000 at the end of each year for five years at 7% compounded annually. (b) $10,000 at the end of each year for eight years at 8% compounded annually. (c) $18,000 at the end of each year for 20 years at 10% compounded annually. (d) $7.000 at the end of each year for 12 years at 12% compounded annually